Mining the earth for hard minerals, such as coal, is one of the oldest formalized endeavors known to civilization. Coal mining companies, together with copper mining, trace their history back in an unbroken pattern for generations. From the earliest times when slaves were used, even through today, mining is a dangerous occupation. The danger lies in several areas, primarily because of the inherent structural weakness caused in the earth as the mineral is removed.
Coal mining poses particular problems mainly because of the depths involved and the tendancy for coal mining to release explosive gases.
Coal, as is well-known, is a vegetation product which has undergone countless years of pressure inside the earth. In some situations, the earth has formed upward and thus the coal may be found in seams inside a hill or mountain. One method of removing this coal is known as strip mining, where the earth and rock covering is stripped away and the exposed coal removed from the seam. Such a procedure eliminates, for the most part, the need for people to enter the earth through tunnels. However, it becomes necessary in a strip mining operation to remove large areas of earth in an effort to uncover the coal. There is, of course, a point beyond which the cost of earth removal exceeds the selling price of the mined coal. When this point is reached, the strip mine is abandoned, even though the seam of coal is not depleted. In some situations, when it becomes uneconomical to strip away the earth covering the coal, large augers are used to bore out coal. Even using the boring method, which results in pockets in which water collects, vast amounts of coal are left unmined. In many situations, especially where the coal seam is less than twenty inches in height, augering is impractical.
Thus, it is readily seen that, especially in an era when energy sources are at a premium, it is desirable to remove as much coal as possible from known coal seams and to do so at the lowest possible cost.
Further compounding the problem is the valid concern for our environment. Abandoned coal mines can be dangerous. Explosive gases may collect or children may somehow find their way inside. Water, which naturally flows into the mines, may become contaminated and run out into our lakes and streams. The list of dangerous possibilities is only limited by one's imagination.
Based on these concerns, stringent laws have been enacted to protect against the possibilities of danger. The sum effect of the laws and the regulations which have been promulgated in support thereof is that mining companies must adhere to strict standards in their mining operations. As the requirements become tougher, the cost of mining operations rise and a point is reached where it becomes uneconomical to mine coal. At that point, everyone is the loser.
For the most part, the environment can be best served, and the regulations are established, to insure that after a hill is strip mined, the earth is restored. Two factors are thereby achieved. First, the environment does not appear scarred and disturbed. And second, tunnels or holes do not remain to fill with acid water. While proper earth restoration is desirable, it still requires a number of years before nature can fully heal the wounds.
Thus, a need exists in the art for a mining technique to be applied which does not leave behind an unsightly or unsafe environment. Such a technique must be economical and must be able to mine the coal at the deepest sections of a mountain, as well as those sections of the coal seam which are near the surface. In addition, such a technique must mine coal seams of varying thicknesses and have a high degree of safety for the miners.